Slide fastener stop



Oct. 12, 1965 R. JENSEN ETAL SLIDE FASTENER STOP 3 Sheets-Sheet 1 Filed July 15, 1963 W NE/ w m E V W.

1965 R. JENSEN ETAL 8 9 SLIDE FASTENER STOP Filed July 15, 1963 3 Sheets-Sheet 2 21 :1 .5. T 1 TH was-Pr JEA/JE/V i El BY 4/1 45 w EMA/yaw? Oct. 12, 1965 R. JENSEN ETAL SLIDE FASTENER STOP 3 Sheets-Sheet 3 Filed July 15, 1963 United States Patent 3,210,819 I SLIDE FASTENER STOP Robert Jensen, New Britain, and Charles W. Elsenheimer, Meriden, Conn., assignors to Prentice Corporation, Kensington, Conn., a corporation of Connecticut Filed July 15, 1963, Ser. No. 294,928 18 Claims. (Cl. 24-20511) This invention relates to the manufacture of separable fasteners of the type in which series of locking elements arranged on opposed edges of stringer tapes are interlocked and disengaged by a slider movable lengthwise along the stringers.

The art has been seeking for some time a satisfactory fastener of the indicated type which can be rapidly opened from a locked position without danger of the locking means on the slider thereof catching during such opening operation and which can be laundered without causing destruction to the garment on which it is mounted. It was known that such a satisfactory fastener should be provided with a locking slider which is not dependent for its locking action on pins or cams actuated by the pull tab, and which could be opened quickly from a locked position without danger of the slider inadvertently catching on the stringers in its opening movement, simply by pulling outwardly on the stringers above the slider. The art has devised several types of fasteners capable of accomplishing this purpose, but the fasteners so far de vised have for various reasons proved unsatisfactory and are not employed commercially to any great extent.

It is the principal object of the present invention to provide an improved fastener in which the slider can be locked in a given position on the stringers until positively disengaged therefrom without the use of locking means associated with the pull tab, and in which the slider can be put into free slide condition and rapidly opened from such locked position by a quick lateral pull on the stringers above the slider without danger of the latter jamming or being caught in the stringers.

Another object of the invention is to provide an improved means for locking the slider at the given position with a positive snap action that makes the user consciously aware of its occurrence.

A further object of the invention is to provide an improved slider locking means of the indicated type which is sturdy and stands up well in usage for a long period.

Other objects of the invention as well as the advantages and features of novelty thereof will become apparent from the following description when read in connection with the accompanying drawings, in which FIG. 1 is a plan view of one end portion of a separable fastener embodying the invention, the slider being shown in unlocked condition adjacent to the locking means provided on one of the stringers;

FIG. 2 is a section taken along the line 22 of FIG. 1;

FIG. 3 is a section taken along the line 33 of FIG. 1 and illustrates the constructions of the cooperable locking means of the slider and stringer;

FIG. 4 is a sectional view similar to FIG. 3, but showing the locking means of the slider interlocked with the stringer locking means;

FIG. 5 is an exploded view showing in plan the interior sides of the slider plates;

FIG. 6 is a plan view of one end portion of a fastener stringer provided with a modified form of locking means;

FIG. 7 is a section taken along the line 7-7 of FIG 6;

FIG. 8 is a view similar to FIG. 7 but showing the form of the parts as they are assembled;

FIG. 9 is a view similar to FIG. 6 showing another embodiment of stringer locking means;

FIG. 10 is a section taken along the line 10-10 of FIG. 9;

3,210,819 Patented Oct. 12, 1965 FIG. 11 is a vertical sectional view of a slider similar to the view of the slider shown in FIG. 3 and showing a modified form of the locking means provided in the slider.

FIG. 12 is a vertical sectional view of a further embodiment of the invention;

FIG. 13 is a perspective view of an open mold illustrating one step in the method of making the locking device of this invention;

FIG. 14 is a front perspective view of the front half of the mold; and

FIG. 15 is a perspective view of the mold closed and ready for the injection operation.

Referring now more particularly to FIGS. 1 to 5 of drawings, the reference numerals 10 and 11 designate the closed or upper end portions of two stringers of a separable fastener. The opposed beaded edges of the stringers are provided with the usual rows or series of suitable locking elements 12 and 13, respectively, which interlock in the usual manner, and which are adapted to be interlocked and disengaged by a slider 14 movable longitudinally of the stringers. Located at the upper end of the stringer 11 is a locking device generally designated 15 and adapted to cooperate with locking means in the slider generally designated 16 to secure or lock the slider in position at the closed or upper end of the fastener.

The locking device 15 is composed of the last three end locking elements 13 at the upper end of the series 13 thereof and a suitable hard compressible moldable material uniting such elements together into a single member having a cross-sectional area similar to that of the locking elements. Two of the locking elements 13' form the end walls of such member and the third element is embedded in the moldable material at the central portion of such member. The moldable material entirely fills the spaces between the locking elements 13', enclosing the portions of the associated stringer head 21 therebetween, and covers the exterior surfaces of such locking elements. The moldable material is formed to provide two dome-shaped projections 20 on the outer and inner surfaces of the device over the sides of the central locking element 13'. The bases of the projections 20 span the sides of the central locking element and are integral with the moldable material between the locking elements. It is preferred that the moldable material be a plastic such as nylon and Teflon as these materials have good abrasive resistance and high resistance to heat, and are resilient i.e., will give under pressure and will return to their molded configurations when the pressure is relieved without taking a permanent set. In this connection, applicants have found that when the inter-engageable surfaces of the locking device 15 and of the slider locking means 16, are both made of hard, non-resilient materials, such as metal, the useful life expectancy of such locking means is very short and not sufliciently long enough to make the fastener commercially practical. After further experiment, applicants found that in order to accomplish the purposes of their invention it is critical that not only must such surfaces be configured to operate with a cam-like snap action, but that one of such surfaces must be constituted of a compressible, resilient material capable of reducing the abrasive resistance of such surfaces to a minimum. It has been found that plastic materials such as nylon and Teflon best accomplish the purposes of the invention. A suitable nylon is that now being manufactured by E. I. du' Pont de Nemours and Co. under the name Zytel.

The slider 14 as is usual comprises a top or outer wall 25 and a bottom or inner wall 26 united together by a substantially V-shaped neck portion 27 wihch divides the slider at the wide end thereof into two diverging channels 28, 29 that merge into a single channel below the neck portion 27 and extending through the lower, narrower end of the slider. The outer side edges of the walls 25, 26 are provided with the usual flanges 25', 26' which cooperate with the U-shaped neck portion 27 to interlock or disengage the locking elements 12, 13 in the usual manner. The upper end portions of the walls 25, 26 fo'rniingthe channel 29 are each provided with closed recesses 33 formed in the inner sides thereof adjacent to the neck portion 25 and to the top edges of such wall portions. As is shown more clearly in FIGS. 3-5, the recesses 33 have a configuration or contour substantially the same as that of the dome-shaped projections 20 with the depth of each recess 33 being substantially equal to the height of its associated projections 20. It will thus be apparent that each recess 33 will snugly receive a dome-shaped projection 20 with the apex of the latter in engagement with the inner wall 34 of the recess. It has been found that when the contacting walls of the projections 20 and recesses 33 are comparable a better locking action is provided because the similar contours induce sufiicient additional friction as to build up the load to the extent that looking and unlocking of such parts requires more effort than when such contours are not the same. Further, by making such contacting walls similar, mutilation of a projection 20 when entering (locking) or leaving (unlocking) its associated recess 33 is reduced to a minimum. Entry to each closed recess 33 is afforded by a recessed ramp 35 on which rides its associated projection 20 when the device enters channel 29 of the slider as the slider is closed. The surface of the ramp 35 on which rides the projection 20, in crosssection, has a concave contour complementing the crosssectional contour of the projection 20, and in longitudinal section is convexly shaped so that a prolongation of such section into the recess 33 has a sinuous configuration. It will be noted that the outer or entry end 36 of the ramp 35 is closer to the outer surface of the plate in which it is provided than the inner Wall 34 of the recess 33, but that the remainder of the ramp surface is farther from such outer plate surface than the recess inner Wall 34.

It will be apparent from the foregoing that as the slider is moved to the top of the fastener by manual manipulation of the pull tab 40 provided thereon, the locking device 15 will enter into the slider channel 29. As the upward movement of the slider is continued, the compressible projections will engage the ramps and be compressed by the opposed convexly-shaped cam surfaces of the latter. As the projections pass over the apexes of the ramps 35, they will snap into the recesses 33 with a noticeable click which advises the user that the slider is now locked. The compression on the projections being released as soon as they enter into the recesses 33, the projections return to their normal shape and cooperate with the side walls of the recess to lock the slider 14 against movement longitudinally on the stringers. This locking action is enhanced by making the width of each ramp less than the length of the top wall of its assoicated recess, a construction that is rendered possible by the dome-shaped configuration of the projections 20. On the other hand, when the pull tab is pulled to release the slider from the locking device 15, the locking projections 20 will again be forced between the opposed cam-like surfaces of the ramps and as they are compressed will automatically ride out between such ramps to free the slider. The fastener may then be quickly opened by spreading apart the upper ends of the stringers.

From a consideration of the foregoing, it will be apparent to those skilled in the art that the invention may be practiced with other forms of locking means without departing from the concept underlying the structures shown in FIGS. 1 to 5 of the drawings. Thus instead of constructing the locking device 15 by molding together a plunality of locking elements with plastic material, the locking device may be specially constructed in the manher of the device designated generally 15 in FIG. 6 of the drawings. As is shown more clearly in FIGS, 7 and 8 of the drawings, this modified locking device 15 may comprise an elongated rectangularly-shaped member having jaws 46, 46 to .be clamped onto the beaded edge 21 of the stringer 11. The jaws 46, 46 are preferably provided along the inner edges of their outer ends with series of teeth 47 to assure a firmer grip of the member 45 to the stringer. The member 45 is provided centrally with a vertical opening 49 that extends through both the body of such member and the jaws 46 thereof. As is shown in FIG. '8, the opening 49 is formed prior to the assembly of member 45 onto the stringer 11 and while the jaws are in a spread condition, so that it is cylindricallyshaped as long as the jaws remain in such condition. The diameter of this opening is such that in insert 48 is a slip fit therein and may be slidiably assembled on the member 45 through such opening 49 in the manner indicated in full lines in FIG. 8 until it reaches the dotted line position shown in such figure. It will be noted that the body of the insert 48 has a concave configuration to enable a proper seating of the stringer bead 21 between the jaws 46 of the member 45 when the assembled member 45 is attached to the stringer 1 1. 1T his dumbbell configuration of the insert 48 is also utilized in permanently securing the insert to the member 45. The member 45 is provided along its outer wall with a groove 50 which facilitates the positioning of a staking tool to upset the material of member 45 into the opening 49 and the space provided by the concave configuration of the body of the insert 48, such upset stock thus locking the dumbbell 48 in its seated position on the member 45. This operation is preferably performed before the jaws 46 are closed on the stringer head 21. In the assembled condition of the parts 45, 48 on the stringer 11, as shown in FIGS. 6 and 7, there will be presented dome-shaped projections 20' which function in the manner previously described with respect to the projections 20. The insert 48 and the ends 20 thereof are made of suitable moldable material having the characteristics of the material constituting the projections 20 and preferably constituted of nylon or Teflon.

In the embodiment shown in FIGS. 9 and 10 of the drawings, the locking device 15" is constituted wholly of a single piece of material formed so that it is provided with an exterior configuration substantially similar to those of the locking devices 15 and v15'. The locking device 15 may be made wholly of suitable plastic material having the characteristics of the plastic material forming the locking projections on the previously described locking devices. It may also be made of metal, in which case the interengageable surfaces of the locking means provided in the slider, and especially the ramp surfaces between which the locking projections of the locking device pass as they move toward the locking recesses 33, in accordance with the invention, should be made of material having the desired characteristics of nylon and Teflon. This may be accomplished by making the associated slider entirely of suitable plastic material, or as is shown in FIG. 11 of the drawings, by inserting into suitable recesses provided in the inner sides of the walls of the slider 14', inserts 55, of suitable plastic material and formed to provide the locking recesses and ramp surfaces described in the embodiment of FIGS. 1 to 5.

It is within the contemplation of the invention to attain the desired compressible, resilient action of one of the locking members by making either the locking device 15 or the associated slider locking means, of resilient construction, rather than of resilient material. Thus as is shown in FIG. 12 of the drawings, the locking element may be composed of a body portion 58 having locking jaws 59, 59 and two balls 60, 60 and a spring 6 1 assembled in an opening in the body portion 58 in a manner known to those skilled in the art. It is believed to be evident that the spring pressed balls 60, 60 will function in a manner similar to the projections 20 of the device 15 to accomplish the purposes of the invention.

In accordance with the invention, the locking device illustrated in FIGS. 1 to 4 of the drawings is made with the use of a suitable plastic injection machine of known construction and as illustrated in FIGS. 13 to 15 of the drawings provided with two cooperating mold halves adapted to mold the locking devices 1'5 successively in a step-by-step fashion on a continuous length of tape 65 provided with a plurality of spaced series 66 of locking elements. It will be understood that in making the fasteners, the tape 6'5 will be cut into length-s each of which will be provided with one complete series 66 of locking elements. For the purposes of illustration, the mold halves are constructed to form the locking devices using the three locking elements .67 in each series 66 which are adjacent to the two top elements 68 in each such series. Each section of tape with its associated series 66 of looking elements is advanced by the operator into molding position when the mold isopened. As is shown in FIGS. '13 and 14, the back mold half 69 and the front mold half 70 are provided with mating grooves 71, 72 respectively, to receive the locking elements. In the use of the mold, the operator pulls the tape through the groove or channel '71 until a locating insert 73 which is provided on the back mold half 69 and extends into the path of movement of the series 66 of locking elements being advanced comes into contact with the top element 6-8 in such advancing series. The front half 70 of the mold will then be moved to close the mold and to bring the locating inserts 74, '74 thereof into the space between the groups of elements 67, 68 and between the lowermost element 67 and the next succeeding element in the series, thus fixing the positions of the two end elements 67 to be included in the locking device. In the closing movement of the molds, the insert 73 will enter a groove 75 provided in the front mold half 70 and the inserts 74, 74 will enter the grooves 76, 7 6 on the rear mold half 69. When the mold is closed the three elements "67 will form with the sides of the grooves "71, 72, a mold cavity for the plastic material. It will be noted that the back mold half 69 below the groove 71 'will grip a portion only of the width of the tape '65 and below that is relieved so that the longitudinal edge portion of the tape not provided with the locking elements is not tightly gripped between the two mold halves, thereby preventing hanging lint and threads from interfering with the operation of the mold. After the mold is properly closed on a tape section as shown in FIG. 15, the nozzle 77 of the plastic injection machine deposits a charge of the desired plastic material in the said mold cavity. When the mold again opens the operator may pull the series of locking elements on which the locking device 15 has been formed out of the groove 71 and advance the next series 66 of locking elements to repeat the process. The gate 7 8 that is left on the formed locking device I1 5 may be removed in any suitable manner while the operator is waiting for the mold to go through its cycle on the next succeeding series 66 of locking elements.

It will be evident to those skilled in the art that various modifications in the hereinabove described invention may be made without departing from the spirit thereof or the scope of the appended claims.

We claim:

1. In a slide fastener, :a pair of stringers having series of locking elements along their opposed edges, a slider having diverging channels formed between the walls thereof at its upper, wider end and movable along said elements for interlocking and disengaging the same and cooperating means on one of said stringers :and said slider for locking the latter against movement in a given position on the stringers, said cooperating means comprising a locking member having at least one locking projection secured on said one stringer at said given position and adapted to enter the upper end of one of said diverging channels, a recess to receive said locking projection in at least one wall of said one diverging channel adjacent 6 to the upper end of said diverging channel and located in the path of movement of said locking member, said recess including an enlarged inner end portion having a configuration approximating the configuration of said locking projection to receive said locking projection therein and having a depth greater than the remainder of said recess, and including a portion connecting said inner end portion to the upper end of said diverging channel :and having an inner locking projection engaging surface convexly curved in the direction of the movements of said locking projection toward and away from said inner end portion to provide a ramp member having an apex located intermediate said inner end portion and said upper channel end, one of said locking and ramp members being a compressible, resilient member, and the apex of said ramp member being spaced from the interior surface of the other channel wall a distance less than the overall height of said locking member so that said resilient member is compressed as said locking member moves over the apex of said ramp surface in passing through said recess in one direction or the other, said ramp member being configured to retain said locking projection in said inner end portion of the recess until positively moved therefrom.

2. In a slide fastener such as defined in claim K1, in which said locking projection is dome-shaped, said enlarged inner end portion of the recess has a partially spherical configuration, and said recess as :a whole has in longitudinal section a substantially sinuous configuration.

3. In a slide fastener such as defined in claim 1, in which said locking projection consists of compressible, resilient plastic material.

t. In a slide fastener such as defined in claim '1, in which said locking member comprises a holder provided with jaws clamped to said stringer edge and is provided with a transverse opening partially offset with relation to said stringer edge, and an insert of compressible, resilient plastic material extending through .said opening and intermediate its ends being recessed to receive said stringer edge and thereby be locked by the latter in said opening, said locking projection being provided on one end of said insert.

5. In .a slide fastener such as defined in claim 4, in which said jaws are provided on the inner side of each outer edge thereof with :a series of holding teeth engageabl-e with said stringer edge and providing a supple mentary grip on the latter.

6. In a slide fastener such as defined in claim 4, in which the ends of said insert engage with the material of said holder forming the outer ends of said transverse opening to lock said insert in proper position in said holder.

7. In a slide fastener such as defined in claim 6 in which the material of said holder intermediate the ends of said transverse opening is upset to secure said insert permanently in said holder.

8. In a slide fastener such as defined in claim 1, in which said locking member consists of compressible, resilient plastic material.

9. In a slide fastener such as defined in claim :1, in which said locking projection consists of compressible, resilient, plastic material, and said ramp member consists of rigid material.

10. In a slide fastener such as defined in claim 1, in which said convexly curved surface of said ramp is further away from the interior surface of the other channel wall at its outer end than at its inner end, the inner end of said ramp forming part of the side walls of said enlarged inner end portion of the recess.

11. In a slide fastener such as defined in claim 10, in which the opening of the inner end portion of the recess has a width approximating the overall width of said locking projection, and the inner end of said ramp has a width less than the Width of said inner end portion of the recess and less than the overall width of said locking projection.

12. A slider for locking engagement with locking means secured in a given position on one of the stringers of a separable fastener, said slider comprising spaced walls defining a channel having diverging arms at the upper, wider end thereof, a locking recess in at least one wall of one of said channel arms adjacent to the upper end of said channel arm and located in the path of movement of the stringer locking means into said channel arm, said recess including an enlarged inner end portion having a configuration approximating the configuration of the stringer locking means to receive said locking means therein and having a depth greater than the remainder of said recess, and including a portion connecting said inner end portion to the upper end of said channel arm, and having an interior surface convexly curved in the direction of the movements of the stringer locking means toward and away from said inner end portion to provide a ramp member having an apex located intermediate said inner end portion and said upper end of the channel arm, and the apex of said ramp member being spaced from the interior surface of the other channel wall a distance less than the overall height of said stringer locking means, said ramp member being configured to retain said stringer locking means in engagement with said recess until positively removed therefrom.

13. A slider such as defined in claim 12, in which said convexly curved surface of said ramp is farther away from the interior surface of the other channel wall at its outer end than at its inner end, the inner end of said ramp forming part of the side walls of said enlarged inner end portion of the recess.

14. A slider such as defined in claim 13, in which the opening of the inner end portion of the recess has a width approximating the overall width of said stringer locking means, and the inner end of said ramp has a width less than the width of said inner end portion of the recess and less than the overall width of said locking projection.

15. In a slide fastener, a pair of stringers having series of locking elements along their opposed edges, a slider having diverging channels formed between the walls thereof at its upper, wider end and movable along said elements for interlocking and disengaging the same, and coperating means on one of said stringers and said slider for locking the latter against movement in a given position on the stringers, said cooperating means comprising a locking member having at least one locking projection secured on said one stringer at said given position and adapted to enter the upper end of one of said diverging channels, a closed recess to receive said locking projection in at least one wall of said one diverging channel adjacent to the upper end of said diverging channel and located in the path of movement of said locking member, and a ramp member connecting the upper end of said recess to the upper end of said diverging channel, said locking member being composed of a plurality of fastener locking elements, and compressible, resilient moldable material bonding said locking elements together to form a unitary member, said locking projection being formed of said moldable material, and said ramp member having a locking projection engaging surface convexly curved in the direction of the movement of said locking projection toward said recess and part of which is spaced from the interior surface of the other channel wall a distance less than the overall height of said locking member so that said resilient projection is compressed as said locking member moves over said ramp surface, said ramp member being configured to retain said locking projection in said closed recess until positively moved therefrom.

16. A stringer for a slide fastener composed of a pair of stringers having a series of locking elements along their opposed edges, and a slider for interlocking and disengaging said locking elements and having a pair of spaced walls, at least one of which is provided adjacent to the upper end thereof with a closed locking recess located in the path of movement of stringer locking elements between said slider walls, said stringer having on said opposed edge thereof a locking member adapted to enter the upper end of the fastener slider and interengage with said locking recess thereof to lock such slider against movement in a given position on said stringer, said locking member comprising a locking projection engageable with said locking recess to eifect said locking action, and composed of compressible, resilient, moldable material enabling such projection to be compressed as it moves between the slider walls to such locking recess and configured to retain said locking projection in such locking recess until positively removed therefrom, said locking member being composed of a plurality of fastener locking elements, and compressible, resilient moldable material bonding said locking elements together to form a unitary member, said locking projection being formed of said moldable material.

17. In a slide fastener, a pair of stringers having series of locking elements along their opposed edges, a slider having diverging channels formed between the walls thereof at its upper, wider end and movable along said elements for interlocking and disengaging the same, and cooperating means on one of said stringers and said slider for locking the latter against movement in a given position on the stringers, said cooperating means comprising a locking member having at least one locking projection secured on said one stringer at said given position and adapted to enter the upper end of one of said diverging channels, a closed recess to receive said locking projection in at least one wall of said one diverging channel adjacent to the upper end of said diverging channel and located in the path of movement of said locking member, and a ramp member connecting the upper end of said recess to the upper end of said diverging channel, said locking projection consisting of rigid material, and said ramp member consisting of compressible, resilient, plastic material and having a locking projection engaging surface convexly curved in the direction of the movement of said locking projection toward said recess and part of which is spaced from the interior surface of the other channel wall a distance less than the overall height of said locking member so that said resilient ramp member is compressed as said locking member moves over said ramp surface, said ramp member being configured to retain said locking projection in said closed recess until positively moved therefrom.

18. In a slide fastener such as defined in claim 17, in which said ramp member forms part of a plastic insert mounted in said one wall of said diverging channel.

References Cited by the Examiner UNITED STATES PATENTS 1,901,257 3/33 Norton 24205.11 2,112,725 3/38 Carlile 24205 .11 2,157,381 5/39 Carlile 24205.11 2,263,920 11/41 Dau 1859 2,578,442 12/ 51 Morin 24205. 11 2,731,671 1/56 Zimmerman 18-59 2,832,119 4/58 Neitlich 24205.11 2,900,694 8/59 Brown 24205 .1 1

FOREIGN PATENTS 474,228 6/51 Canada.

659,627 7/29 France. 1,061,708 4/54 France.

550,802 1/ 43 Great Britain.

DONLEY J. STOCKING, Primary Examiner.

BERNARD A. GELAK, Examiner. 

1. IN A SLIDE FASTENER, A PAIR OF STRINGERS HAVING SERIES OF LOCKING ELEMENTS ALONG THEIR OPPOSED EDGES, A SLIDER HAVING DIVERGING CHANNELS FORMED BETWEEN THE WALLS THEREOF AT ITS UPPER, WIDER END AND MOVABLE ALONG SAID ELEMENTS FOR INTERLOCKING AND DISENGAGING THE SAME AND COOPERATING MEANS ON ONE OF SAID STRINGERS AND SAID SLIDER FOR LOCKING THE LATTER AGAINST SAID MOVEMENT IN A GIVEN POSITION ON THE STRINGERS, SAID COOPERATING MEANS COMPRISING A LOCKING MEMBER HAVING AT LEAST ONE LOCKING PROJECTION SECURED ON SAID ONE STRINGER AT SAID GIVEN POSITION AND AADAPTED TO ENTER THE UPPER END OF ONE OF SAID DIVERGING CHANNELS, A RECESS TO RECEIVE SAIDLOCKING PROJECTION IN AT LEAST ONE WALL OF SAID ONE DIVERGING CHANNEL ADJACENT TO THE UPPER END OF SAID DIVERGING CHANNEL AND LOCATED IN THE PATH OF MOVEMENT OF SAID LOCKING MEMBER, SAID RECESS INCLUDING AN ENLARGED INNER END PORTION HAVING A CONFIGURATION APPROXIMATING THE CONFIGURATION OF SAID LOCKING PROJECTION TO RECEIVE SAID LOCKING PROJECTION THEREIN AND HAVING A DEPTH GREATER THAN THE REMAINDER OF SAID RECESS, AND INCLUDING A PORTION CONNECTING SAID INNER END PORTION TO THE UPPER END OF SAID DIVERGING CHANNEL AND HAVING AN INNER LOCKING PROJECTION ENGAGING SURFACE CONVEXLY CURVED IN THE DIRECTION OF THE MOVEMENTS OF SAID LOCKING PROJECTION TOWARD AND AWAY FROM SAID INNER END PORTION TO PROVIDE A RAMP MEMBER HAVING AN APEX LOCATED INTERMEDIATE SAID INNER END PORTION AND SAID UPPER CHANNEL END, ONE OF SAID LOCKING AND RAMP MEMBERS BEING A COMPRESSIBLE, RESILIENT MEMBER, AND THE APEX OF SAID RAMP MEMBER BEING SPACED FROM THE INTERIOR SURFACE OF THE OTHER CHANNEL WALL A DISTANCE LESS THAN THE OVERALL HEIGHT OF SAID LOCKING MEMBER SO THAT SAID RESILIENT MEMBER IS COMPRESSED AS SAID LOCKING MEMBER MOVES OVER THE APEX OF SAID RAMP SURFACE IN PASSING THROUGH SAID RECESS IN ONE DIRECTION OR THE OTHER, SAID RAMP MEMBER BEING CONFIGURED TO RETAIN SAID LOCKING PROJECTION IN SAID INNER END PORTION OF THE RECESS UNTIL POSITIVELY MOVED THEREFROM. 